The automation of plastics processes such as plastics extrusion, compounding and resin manufacturing can be done with bulk material handling equipment and controls. This application profile section provides an in depth look at various plastics processing applications, materials fed in these applications, and components incorporated into a system.

Polyolefin Production
Polyolefins are produced by the polymerization of olefins or alkenes (molecules with the general formula CnH2n) such as ethylene, propylene, butene, isoprene, pentene, etc. The name “olefin" means "oil-like" and refers to the oily character of the materials. The most important commercial polyolefins are polyethylene (PE), polypropylene (PP) and ethyl vinyl acetate (EVA). Polyethylene is classified according to its density as Very Low Density Polyethylene (VLDPE), Low Density Polyethylene (LDPE), Linear Low Density Polyethylene (LLDPE), Medium Density Polyethylene (MDPE), and High Density Polyethylene (HDPE).

Polyethylene and polypropylene are two of the top polymer resins used in the world today. These resins can be tailored to achieve wide range of mechanical and chemical properties, making it possible to use them in a myriad of applications such as agricultural films, garments, tapes, stretch films, retail bags, bottles, containers, pipes, etc.

The selection of a polyolefin for a particular application depends on the resin’s type and grade, which are determined by the manufacturing technology or process, the catalyst, and the raw feedstock used in production. In turn, the polyolefin grade is determined by key properties such as molecular weight, molecular weight distribution (MWD), crystallinity, branching and density that affect how and where each resin is used.

PVC Production
Polyvinyl chloride, commonly known as PVC, is one of the most widely used thermoplastics for several good reasons. PVC has an excellent cost/benefit ratio when compared to other polymer resins.

PVC is used in the manufacture of end-use products for a wide range of applications in the consumer, construction, food and medical industries. Products made with PVC exhibit good impact strength, stiffness and strength-to-weight ratio. PVC products offer good dimensional stability at ambient temperatures, resistance to chemicals and oils, durability, and non-flammability character.

PVC is produced by the polymerization of VCM (vinyl chloride monomer). This reaction is carried out in an autoclave where the raw materials (VCM, emulsifiers and chemical initiators) are dispersed in demineralized water under vigorous agitation. There are four well known methods for the production of PVC: suspension (S-PVC), emulsion (E-PVC), micro suspension and mass polymerization. The suspension polymerization process is the most commonly used

Wood-Plastic Composites
Wood-plastic composites may be one of the most dynamic sectors of today's plastic industry. Although the technology is not new, there is growing interest in the new design possibilities this mariage of materials offers.

The production of Wood-Plastic Composites typically uses a fine wood waste (cellulose based fiber fillers such as hardwood, softwood, plywood, peanut hulls, bamboo, straw, etc.) mixed with various plastics (PP, PE, PVC). The powder is extruded to a doughlike consistency and then extruded to the desired shape. Additives such as colorants, coupling agents, stabilizers, blowing agents, reinforcing agents, foaming agents, and lubricants help tailor the plastic end product to the target area of application.

Long Fiber Reinforced Thermoplastics
Long Fiber Reinforced Thermoplastics are the buzz of the auto industry in Europe and the US and are one of the most important trends in the plastics industry today. Long Fiber Reinforced Thermoplastics are a recent development in newer technologies where PP or thermoplastic material is directly compounded with long glass fibers (rovings) and then molded in tne operation.

Glass fibers of ½" (12 mm) up to 2" (50 mm) length give much higher stiffness, strength and toughness than the 1/8" (3 mm) fibers that have been used for reinforcement for decades. Long Fiber Reinforced Thermoplastics (LFT) have excellent mechanical properties and stiffness-to-weight ratio which is of great interest to the automotive industry. These in-line compounding processes for long fiber material offer users more flexibility, as they are able to both compound and process such materials in accordance with their own formulation and also use ready made compounds.

Calcium Carbonate in Plastics Compounding
Calcium carbonate (CaCO3) is one of the most popular mineral fillers used in the plastics industry. It is widely available around the world, easy to grind or reduce to a specific particle size, compatible with a wide range of polymer resins and economical. As an additive in plastic compounds, CaCO3 helps decrease surface energy and provides opacity and surface gloss, which improves surface finish. In addition, when the particle size is carefully controlled, CaCO3 helps increase both impact strength and flexural modulus (stiffness).

Calcium carbonate may be used with a myriad of thermoplastic resins. Polypropylene compounds are often filled with calcium carbonate to increase rigidity, an important requirement for operations at high temperatures. In PVC, calcium carbonate is used with flexible compounds such as tubing, wire and cable insulation, latex gloves, trash bags and in rigid compounds such as extruded pipes, conduits and window profiles.

BOPP Film Production
Growth in commodity and specialty biaxially-oriented films for the packaging industry has been steadily growing, with applications requiring simultaneous feeding of a large variety of additives directly into the extruder. The worldwide film demand is steadily growing. Growth in biaxially-oriented films for the packaging industry is especially strong.

Biaxially-oriented films can be divided into two categories:

Commodity films, which need to be produced as cost-efficiently as possible due to strong price pressure from the market

Specialty films, where a higher price is possible, however this is usually related to higher demands in technology and therefore also higher production costs

There is a clear trend in specialty film production to multi-layer film types, where more and more co-rotating twin screw extruders are utilized. This enables film manufacturers to simultaneously feed a large variety of additives directly into the extruding process, increasing flexibility and reducing production costs. This is very beneficial in the production of multi-layer high barrier films, balanced shrink films, etc.

Adhesives are characterized by the fact that they adhere simply through pressing together the parts of the joint which requires bonding. They demonstrate a lasting and permanent adhesive effect at room temperature. Hot melt adhesives are solventfree adhesives, which are characteristically solid at temperatures below 180°F (82°C), are low viscosity fluids above 180°F, and set rapidly upon cooling. The development of hot melt adhesive technology stemmed from the previous use of molten wax for bonding. When this method no longer satisfied performance needs, 100% thermoplastic systems were introduced. Today, hot melt adhesives are used in a variety of manufacturing processes, including bookbinding, product assembly, and box and carton heat sealing. There are a number of hot melt adhesives in use, with the most common being those used for hot melt pressure sensitive adhesive applications.